Touch sensor electrode driving

Abstract

In one embodiment, a controller includes a processor and a memory, the memory storing logic. The logic is configured to perform, when executed by the processor, operations comprising detecting, in response to driving electrodes of a touch sensor with a first drive signal having a first polarity, a presence of a stylus. The presence of the stylus is detected based on a first sense signal, the first sense signal having a second polarity. The operations further comprise detecting, in response to driving the electrodes with a second drive signal having the first polarity, a second sense signal having a third polarity. The third polarity is an inverse of the second polarity. The operations further comprise driving, in response to detecting the second sense signal having the third polarity, the electrodes with a third drive signal having a fourth polarity. The fourth polarity is an inverse of the first polarity.

What is claimed is: 
     
       1. An apparatus, comprising:
 a touch sensor comprising a plurality of electrodes; and 
 a controller configured to perform operations comprising:
 driving the plurality of electrodes with a first drive signal having a first polarity; 
 detecting, in response to driving the plurality of electrodes with the first drive signal having the first polarity, a presence of a stylus, the presence of the stylus detected based on a first sense signal, the first sense signal having a second polarity; 
 driving the plurality of electrodes with a second drive signal having the first polarity; 
 detecting, in response to driving the plurality of electrodes with the second drive signal having the first polarity, a second sense signal, the second sense signal having a third polarity, the third polarity being an inverse of the second polarity; and 
 driving, in response to detecting the second sense signal having the third polarity, the plurality of electrodes with a third drive signal having a fourth polarity, the fourth polarity being an inverse of the first polarity. 
 
 
     
     
       2. The apparatus of  claim 1 , wherein the controller is further configured to perform operations comprising detecting, in response to driving the plurality of electrodes with the third drive signal having the fourth polarity that is the inverse of the first polarity, a presence of the stylus, the presence of the stylus detected based on a third sense signal, the third sense signal having the second polarity. 
     
     
       3. The apparatus of  claim 2 , wherein the controller is further configured to perform operations comprising:
 driving the plurality of electrodes with a fourth drive signal having the third polarity; 
 detecting, in response to driving the plurality of electrodes with the fourth drive signal having the third polarity, a fourth sense signal, the fourth sense signal having the third polarity; and 
 driving, in response to detecting the fourth sense signal having the third polarity, the plurality of electrodes with a fifth drive signal having the first polarity. 
 
     
     
       4. The apparatus of  claim 2 , wherein:
 detecting the presence of a stylus based on the first sense signal comprises detecting that a first peak of the first sense signal has the second polarity and meets a proximity detection threshold; and 
 detecting the presence of the stylus based on the third sense signal comprises detecting that the third sense signal has the second polarity and meets the proximity detection threshold. 
 
     
     
       5. The apparatus of  claim 1 , wherein the first polarity and the second polarity are the same polarity. 
     
     
       6. The apparatus of  claim 1 , wherein the first polarity and the second polarity are a positive polarity. 
     
     
       7. The apparatus of  claim 1 , wherein the third polarity and the fourth polarity are the same polarity. 
     
     
       8. The apparatus of  claim 1 , wherein the third polarity and the fourth polarity are a negative polarity. 
     
     
       9. The apparatus of  claim 1 , wherein the plurality of electrodes comprises:
 a first plurality of electrodes extending in a first direction; and 
 a second plurality of electrodes extending in a second direction. 
 
     
     
       10. A controller, comprising:
 a processor; 
 a memory coupled to the processor and storing logic, the logic configured to perform, when executed by the processor, operations comprising:
 detecting, in response to driving a plurality of electrodes of a touch sensor with a first drive signal having a first polarity, a presence of a stylus, the presence of the stylus detected based on a first sense signal, the first sense signal having a second polarity; 
 detecting, in response to driving the plurality of electrodes with a second drive signal having the first polarity, a second sense signal, the second sense signal having a third polarity, the third polarity being an inverse of the second polarity; and 
 driving, in response to detecting the second sense signal having the third polarity, the plurality of electrodes with a third drive signal having a fourth polarity, the fourth polarity being an inverse of the first polarity. 
 
 
     
     
       11. The controller of  claim 10 , wherein the logic is further configured to perform, when executed, operations comprising detecting, in response to driving the plurality of electrodes with the third drive signal having the fourth polarity that is the inverse of the first polarity, a presence of the stylus, the presence of the stylus detected based on a third sense signal, the third sense signal having the second polarity. 
     
     
       12. The controller of  claim 11 , wherein the logic is further configured to perform, when executed, operations comprising:
 driving the plurality of electrodes with a fourth drive signal having the third polarity; 
 detecting, in response to driving the plurality of electrodes with the fourth drive signal having the third polarity, a fourth sense signal, the fourth sense signal having the third polarity; and 
 driving, in response to detecting the fourth sense signal having the third polarity, the plurality of electrodes with a fifth drive signal having the first polarity. 
 
     
     
       13. The controller of  claim 11 , wherein:
 detecting the presence of a stylus based on the first sense signal comprises detecting that a first peak of the first sense signal has the second polarity and meets a proximity detection threshold; and 
 detecting the presence of the stylus based on the third sense signal comprises detecting that the third sense signal has the second polarity and meets the proximity detection threshold. 
 
     
     
       14. The controller of  claim 10 , wherein the first polarity and the second polarity are the same polarity. 
     
     
       15. The controller of  claim 10 , wherein the first polarity and the second polarity are a positive polarity. 
     
     
       16. The controller of  claim 10 , wherein the third polarity and the fourth polarity are the same polarity. 
     
     
       17. The controller of  claim 10 , wherein the third polarity and the fourth polarity are a negative polarity. 
     
     
       18. The controller of  claim 10 , wherein the plurality of electrodes comprises:
 a first plurality of electrodes extending in a first direction; and 
 a second plurality of electrodes extending in a second direction. 
 
     
     
       19. A method, comprising:
 detecting, in response to driving a plurality of electrodes of a touch sensor with a first drive signal having a first polarity, a presence of a stylus, the presence of the stylus detected based on a first sense signal, the first sense signal having a second polarity; 
 detecting, in response to driving the plurality of electrodes with a second drive signal having the first polarity, a second sense signal, the second sense signal having a third polarity, the third polarity being an inverse of the second polarity; and 
 driving, in response to detecting the second sense signal having the third polarity, the plurality of electrodes with a third drive signal having a fourth polarity, the fourth polarity being an inverse of the first polarity. 
 
     
     
       20. The method of  claim 10 , further comprising detecting, in response to driving the plurality of electrodes with the third drive signal having the fourth polarity that is the inverse of the first polarity, a presence of the stylus, the presence of the stylus detected based on a third sense signal, the third sense signal having the second polarity. 
     
     
       21. The method of  claim 11 , further comprising:
 driving the plurality of electrodes with a fourth drive signal having the third polarity; 
 detecting, in response to driving the plurality of electrodes with the fourth drive signal having the third polarity, a fourth sense signal, the fourth sense signal having the third polarity; and 
 driving, in response to detecting the fourth sense signal having the third polarity, the plurality of electrodes with a fifth drive signal having the first polarity.